1. Field of the Invention
The present invention relates to a power receiving device that wirelessly receives power, a wireless power supply system including the power receiving device, and a wireless power supply method.
2. Description of the Related Art
A wireless power supply technique for wirelessly supplying power from a power supply device to a power receiving device by electromagnetic induction has been developed and come into practical use. In recent years, a wireless power supply technique for supplying power by electromagnetic resonance (electromagnetic resonant coupling) that enables long-distance power transmission as compared to a wireless power supply technique for supplying power by electromagnetic induction has attracted attention. Unlike by electromagnetic induction, by electromagnetic resonance, high power transmission efficiency can be maintained even when the transmission distance is several meters, and power loss due to misalignment of an antenna of a power supply device and an antenna of a power receiving device can be reduced.
Patent Document 1 and Non-Patent Document 1 disclose wireless power supply techniques utilizing electromagnetic resonance.
In electromagnetic resonant wireless power supply disclosed in Patent Document 1 and Non-Patent Document 1, a power supply device and a power receiving device each include two antennas. Specifically, the power supply device includes an antenna to which power is supplied from a power source through a contact and a resonant antenna that is coupled with the antenna by electromagnetic induction. Further, the power receiving device includes a power receiving antenna for supplying power to a load through a contact and a resonant antenna that is coupled with the antenna by electromagnetic induction. When the resonant antenna of the power supply device and the resonant antenna of the power receiving device are coupled with each other by magnetic resonance or electric field resonance, power is wirelessly supplied from the power supply device to the power receiving device.